GNS3 配置Static p2p GRE over IPsec
1、实验拓扑
2、基础网络配置
R1配置：
interface FastEthernet0/0
ip address 12.1.1.1 255.255.255.0
interface FastEthernet1/0
ip address 13.1.1.1 255.255.255.0
R2配置：
interface FastEthernet0/0
ip address 12.1.1.2 255.255.255.0
interface FastEthernet1/0
ip address 172.16.1.254 255.255.255.0
ip route 0.0.0.0 0.0.0.0 12.1.1.1
R3配置：
interface FastEthernet0/0
ip address 13.1.1.3 255.255.255.0
interface FastEthernet1/0
ip address 192.168.1.254 255.255.255.0
ip route 0.0.0.0 0.0.0.0 13.1.1.1
R4配置：
interface FastEthernet0/0
ip address 172.16.1.1 255.255.255.0
ip route 0.0.0.0 0.0.0.0 172.16.1.254
R5配置:
interface FastEthernet0/0
ip address 192.168.1.1 255.255.255.0
ip route 0.0.0.0 0.0.0.0 192.168.1.254
3、配置Static p2p GRE over IPsec
3.1、配置GRE
R2配置：
interface Tunnel2
ip address 1.1.1.1 255.255.255.0
tunnel source 12.1.1.2
tunnel destination 13.1.1.3
R3配置：
interface Tunnel3
ip address 1.1.1.2 255.255.255.0
tunnel source 13.1.1.3
tunnel destination 12.1.1.2
3.2、配置LAN-TO-LAN ×××（此时的ACL与普通的LAN-TO-LAN ×××有差异）
R2配置：
crypto isakmp policy 1
encr 3des
authentication pre-share
group 2
crypto isakmp key cisco123 address 13.1.1.3
crypto ipsec transform-set ccie esp-3des esp-sha-hmac
access-list 100 permit gre host 12.1.1.2 host 13.1.1.3
crypto map mymap 1 ipsec-isakmp
set peer 13.1.1.3
set transform-set ccie
match address 100
interface FastEthernet0/0
crypto map mymap
R3配置：
crypto isakmp policy 1
encr 3des
authentication pre-share
group 2
crypto isakmp key cisco123 address 12.1.1.2
crypto ipsec transform-set ccie esp-3des esp-sha-hmac
access-list 100 permit gre host 13.1.1.3 host 12.1.1.2
crypto map mymap 1 ipsec-isakmp
set peer 12.1.1.2
set transform-set ccie
match address 100
interface FastEthernet0/0
crypto map mymap
3.3、配置动态路由协议（此时私网流量走的都是隧道。）
R2配置：
router ospf 1
network 1.1.1.0 0.0.0.255 area 0
network 172.16.1.0 0.0.0.255 area 0
R3配置：
router ospf 1
network 1.1.1.0 0.0.0.255 area 0
network 192.168.1.0 0.0.0.255 area 0
4、NAT对Static p2p GRE over IPsec的影响
通过上面得知，内网流量走的都是GRE隧道，所以，当NAT应用在物理口时对Static p2p GRE over IPsec是没有影响的。但当NAT应用在Tunnel口时，必须将内网网段排除。
